html,body{
    margin:0px;
    padding:0px;
}
.top{
   height: 50px;
   background-color: green;
   line-height: 50px;
   padding-left:20px;
   color:#fff;
}
.lm-flex{
    display: flex;
    flex-direction: row;
    height: auto;
    position: absolute;
    top:50px;
    bottom: 30px;
    width:100%;
}
.left{
    width:20%;
    background-color: #ddd;
    height: 100%;
}
.main{
    width:80%;
    background-color: aquamarine;
}
.bottom{
    height:30px;
    background-color: brown;
    color:#fff;
    line-height: 30px;
    position: absolute;
    bottom: 0px;
    width:100%;
}